Personal identification apparatus using measured tactile pressure

ABSTRACT

A personal identification system employs a matrix of pressure sensors mounted to a plate having a template of a human hand. When a person&#39;s hand is placed on the plate and overlying the template a pressure profile of the person&#39;s hand is provided. This profile is compared with a stored pressure profile of the same person&#39;s hand. If the pressure points or profiles correlate a positive identification of the person is made.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/004,058, entitled PERSONAL IDENTIFICATION APPARATUS USING MEASUREDTACTILE PRESSURE, filed Dec. 3, 2004, the entire disclosure of which ishereby incorporated by reference as if being set forth in its entiretyherein.

FIELD OF THE INVENTION

The invention in general relates to a personal identification apparatus,and more particularly, to an array of pressure sensors arranged within areplication matrix of a human hand for measuring exerted tactilepressure to enable identification.

BACKGROUND OF THE INVENTION

Personal identification systems presently afford a great number ofsignificant uses. With the increase in security requirements, it isparamount to have both a simple and economical means of identifying aperson. Prior art techniques for identifying an individual includefingerprint identification, the use of biometrics, including DNAsampling and other identification measures. Such measures are invasivetechniques as biometrics require samples of a person's body fluid, hair,and the like. The identification of a person by DNA means is expensiveand time consuming. Other less invasive techniques have also beenproposed for identifying individuals, such as retina scans, for example.However, these techniques require expensive equipment in order toimplement positive and secure identification. Accordingly, a personalidentification apparatus which is economical, simple to utilize, andminimally invasive is highly desirable.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, a replicationmatrix of the human hand is provided on a matrix plate. The matrixcontains a plurality of pressure sensors which are arranged throughoutthe hand matrix and which are operative to produce an output voltageproportional to an exerted pressure when a hand is placed on the plate.A person's hand pressure profile is determined during an enrollmentprocedure when the person positions his hand on the matrix plate.Afterwards the person's profile as applied to the plate is measured andcompared against the stored enrollment values to determine whether ornot the person is the person who he claims to be. The system andapparatus described provides a positive identification of an individualwith minimal invasion.

BRIEF DESCRIPTION OF THE DRAWINGS

Understanding of the present invention will be facilitated byconsideration of the following detailed description of the preferredembodiments of the present invention taken in conjunction with theaccompanying drawings, in which like numerals refer to like parts, and:

FIG. 1 is a top plan view of a replication matrix of the human hand formeasuring an exerted tactile pressure according to the invention.

FIG. 2 is a top plan view of a representative human hand for furtherexplaining the invention.

FIG. 3 is a top plan view of the human hand depicting arrays of pressuresensors located in various areas according to the invention.

FIG. 4 is a diagrammatic view of an enrollment procedure according tothe invention.

FIG. 5 is a diagrammatic view of a comparison measurement systemaccording to the invention.

FIG. 6 is a plan view of a pressure sensor employed in the invention.

FIG. 7 is a plan view of the pressure sensor of FIG. 6 together with aninterconnecting glass wafer layer.

FIG. 8 is a cross sectional view of a typical sensor utilized in thisinvention and positioned between two plates according to the invention.

FIG. 9 is a perspective view of the sensor utilized in the invention.

FIG. 10 is an electrical schematic showing two sensors wired to produceoutput, according to the invention.

FIG. 11 is a schematic diagram depicting an alternate embodiment of thepersonal identification apparatus according to this invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a tactical pressure sensor plate or hand replicationmatrix 10. Essentially the sensor plate 10 includes a configuration of ahand 11. The configuration is a conventional human hand which handreplication or template will accommodate the smallest to the largestshaped hand. The replication matrix 10 is a universal template for thehuman hand. The template 11 will accommodate a wide range of varyinghand sizes as is known. Such replications are familiar and have beenutilized for measuring gloves, for example. Within the plate or handreplication matrix 11 there are positioned numerous pressure sensors.The pressure sensors are positioned and interconnected to provide atactile pressure profile when a person's hand is emplaced upon thescreen or matrix 11. In order to further the explain the operation ofthe present invention and the technical theory behind it, reference ismade to FIG. 2.

FIG. 2 illustrates various areas of the hand which are designated byreference numerals. These reference numerals have been repeated inFIG. 1. In FIG. 2 there is shown the central area of a first digitcommonly known as the “little finger” of a typical hand designated as20B. In FIG. 2 the top area of the finger next to the first digit isdesignated by 19B. The area between the thumb and the first finger ofthe hand is designated as 18B, while another area near the thumb isdesignated as 15B, area 16B is shown which is associated with a portionof the palm while area 17B is also designated which is close to theperson's wrist. The purpose of designating these areas is to illustratethat these areas, while substantially uniform from person to person,have very different characteristics in regard to surface contour, fattycontent, length, and width, for example. There are muscles which arefound in the hand. These muscles differ from person to person and arepronounced in certain areas of the hand as 15B. If a person is active,the area 15B would be more defined and would protrude a greater amountthan for example, area 18B. While these characteristics are indicativeof all people, the extent of the musculature of the hand as well as theextent of the depressions may vary greatly. It is known that thecontours, as for example the map of the hand is quite different fromperson to person. Let us take the example of two people with identicalhand configurations. This is meant that one assumes two people have thesame exact size hand including same size fingers, thumb as well aswidth. Based on the fact that they are different individuals, they willnevertheless have different contours associated with the hand. Forexample, areas 20B, 15B, 18B, 19B will not extend in the Z axis as muchfor one person as for the other. Furthermore, there may be differentdepressions due to different muscle size and different variations of oneperson's hand as compared to another. Secondly, the contours, which aredefined by the typical lines used by fortune tellers such as the line25, are different. Due to many differences the pressure profile of twoidentical size hands will be different. Furthermore, the differenceswill exist no matter how much pressure is applied to the plate 10. Aslong as there is a minimum pressure applied by a person's hand, thepressure transducer assembly will be able to respond to this anddetermine that person's identity as compared to any other person'sidentity. This identification results in the differences between thecontours of a person's hand, as well as the differences in theapplication of pressure applied by each unique hand configuration ofeach individual. Thus, when a different hand is placed on the sensorinstrumented plate 10, a totally different pressure profile is obtained.The hand when placed on the plate will touch and depress the varioussensors in the various areas as indicated for example as 15B, 17B, 18Band so on. While these areas have been depicted only by way of exampleit is understood from the configuration of FIG. 2 that there arepluralities of areas which are unique to each individual's hand.Furthermore, it is also understood that the number of pressuretransducers which are implemented to provide the pressure matrixconfiguration of the hand can be varied according to commoncharacteristics of the human hands. For example, most people have anextended area 17B which essentially is immediately above the wrist.Therefore, there does not have to be as many pressure sensors in thisarea as, for example, there would be in area 16B and 18B, where suchareas could vary greatly depending upon the athletic activity and thestrength of a person. Therefore in order to obtain accurate results, onemay place more pressure transducers in the area 18B than in the area17B. One may not place any pressure transducers in the central areadepicted by dash circle 21B as most people have an extreme depression inthis area, and this area would not normally contact the plate. Thus onecan create a pressure map or pressure profile of a person's hand wherethe pressure map would have transducers emplaced thereon and located asa function of a hand structure. For example in areas where greatdifferences are expected one could emplace a greater number of pressuretransducers. This is shown in FIG. 3 whereby the number of transducersplaced in each area can vary according to the general configuration ofthe average hand. While it is understood that this is one embodiment ofthe present invention, it is also understood that one could also emplacea plurality of pressure transducers at all locations indicative of thematrix replication of the hand 11 as shown and not be concerned withdifferent areas. These hand areas can also be examined via a typicalcomputer scan. The reason that one would want to control the placing oftransducers according to a typical hand configuration is cost. Selectivetransducer placement could greatly reduce the number of transducersrequired to provide a pressure profile. The reduced number would stillgive an accurate measurement of hand pressure and user identification.It is of course understood that the entire hand matrix may be covereduniformly with transducers, as well as transducers could only be placedin designated areas as indicated above. The main objective is to be ableto perform a uniform measurement of the tactile pressure profile exertedby each individual's hand.

In FIG. 3 there is shown a replica of the matrix 11 as depicted inFIG. 1. FIG. 3 shows various areas such as 30 where there is a matrixshown in X-Y format. Essentially at each X-Y intersection of the matrix30 there is placed a pressure transducer. As indicated these pressuretransducers are extremely small and are arranged in a matrix format. Inarea 30, the matrix includes many more pressure transducers than forexample the number of pressure transducers in area 31. In a similarmanner there are more pressure transducers in area 32 than there are inarea 35 and 37. There are less transducers in area 35 than area 30 forxample. As one can ascertain, a general format of pressure as well ascontours exerted by an average hand is accommodated. It is noted that inareas where most people will contact the plate with relatively the sameforce will require less pressure transducers. Area 33 would require lesstransducers than for area 30. Area 33 is the central area of the handwhere minimum contact with the plate is made. Area 30 which is locatedbelow the thumb is an area which will vary from individual to individualand therefore one would want a greater pressure profile resolution inthis area. This will ascertain that the individual's profile is betteraccommodated to give a more accurate reading. While the aboveconsiderations should be apparent to those skilled in the art is alsounderstood that the number of transducers throughout the hand profilecan be the same. As for example one would employ a matrix of transducersas depicted by area 37 and the same matrix of transducers would existthroughout the entire hand profile. However, it is believed that placingtransducers in greater concentrations in one or more areas of the handwhich can vary greatly from individual to individual will provide a morereliable tactile pressure profile for each individual.

Operation of the system of the present invention may be described asfollows: When a hand is emplaced upon the matrix 11 of FIG. 1 it nowcontacts a plurality of pressure transducers which essentially form anarray. A user first contacts the pressure transducer array and isrequested to apply pressure to the plate for a number of differenttimes. The user is also asked to exert three or four different pressureson the plate. An area such as area 30 of FIG. 3 is monitored separatelyto determine a threshold pressure level. This area is monitored so thatone may, for example, determine when a pressure A, B and C is applied tothis area. This can be done by measuring the pressure which will beexplained in FIG. 4. Thus a person in order to be identified must firstenroll and have access to the system. Enrollment involves taking apressure hand print or profile of the person during an enrollment mode.During this enrollment mode the person will be asked to place his handon the matrix 11 and exert a first pressure which can be any arbitraryvalue. The value may be implemented by merely placing the person's handon the plate without exerting any force. The person may be asked to pusha little harder during the second mode B and for example be asked topush even harder during the third mode C. Of course the activation ofthe modes would be automatically monitored by monitoring an area ormultiple areas such as 30, 32 and 37 in order to obtain an overallpressure profile of the person. The area may be monitored according toan applied pressure as 5, 10, 15 psi, for example. These profiles willbe stored in a computer in a conventional manner. The matrix can beutilized to produce an instantaneous pressure profile of a person's handby monitoring all points in a single manner. Alternatively one canmonitor each of the pressure transducers by scanning the pressure matrixas will further be explained.

FIG. 4. shows an enrollment scheme. As indicated each person must have apressure profile implemented and stored in order for him to berecognized. Hence as shown in FIG. 4 a person is associated with an IDor an identification number which may be a PIN in case of businesssecurity or may be a social security number. Thus the system can beutilized to gain access to airports and other public places for securitychecks. It is understood that the personal ID number may be a numberassociated with a corporation so that a person may gain entry to securepremises or given areas by the use of his hand pressure identificationprofile. As one will understand in order to have the ability to identifypeople one must first enroll the person in the system. Shown in FIG. 4 aperson to be enrolled now places his hand on the tactile measuringmatrix 10. In this manner the pressure of the hand is measured asindicated by module 42. Pressure measurements are extremelyconventional. The matrix 11 which is on the screen may have pressuretransducers located throughout the hand configuration or the number ofpressure transducers may be different in various areas. In order for anenrollment to take place one places his hand on the hand matrix and fora normal positioning of the hand pressures will be induced throughoutthe template area. Certain areas such as 40, 41 or other areas designedby A, B, C and D may also be separately monitored for each individual.These areas can be the areas that are particularly different for eachindividual. In any event the entire profile of the pressure exerted by aperson's hand is obtained and stored as a pressure map or profile asindicated in module 43. This pressure profile can be stored in a memoryin digital form or can be stored by any other techniques such as opticalstorage. During the enrollment the person may be asked to exert a secondpressure during a second time. During the second pressure measurementthe entire hand profile is again taken and stored as well as particularareas A, B, C, D if desired. More than two pressure measurements can betaken as indicated by module 45 and therefore the hand pressure profileof this person can be stored for different pressure measurements. Byusing conventional algorithms the pressure profile of a person's handcan now be correlated based on the multiple pressures utilized by thesystem. One obtains a generic pressure profile which, for example, showsthat the person in question exerts a certain pressure in area A ascompared to area B as compared to C as compared to D. Essentially whatis indicated is that the pressures applied in areas A, B, C and D willbe relatively proportional to each other in the same ratio andrelatively independent of the pressure applied. For example, at restbased on the formation of a person's hand or otherwise, the pressureratio exerted between areas A and B will be a given constant. As oneapplies greater pressure the ratio between A and B will remainrelatively the same as well as the ratios between A, B, C and D. In thismanner one does not really have to take a full profile of the person'shand but may take different profiles in regard to different areas asindicated. All these pressure profiles are stored in a computer and areassociated with the personal identification number of the person to beidentified.

The identification process is shown in FIG. 5. Again the person placeshis hand on the replication matrix 10 and the pressure exerted ismeasured as indicated by module 50. As seen the areas A, B, C and D canbe looked at and stored for this person or the entire hand pressureprofile of the person can then be measured. The pressure profile asobtained from the person is now compared with stored values indicativeof the person's enrollment procedures as shown in FIG. 4. One can useconventional and well known algorithms to determine whether or not thecomparison of the stored vales with the actual measured pressure valuescorrelate as indicated by module 53. This is a typical acceptancealgorithm which will confirm that the pressure points exerted by thisperson are indicative of the pressure points stored during theenrollment procedure of the person. Essentially such algorithms are wellknown, and are utilized in speech processing and other systems tocorrelate data with previously stored data. Thus the system will acceptthis person and provide legitimate identification based on the pressureprofile exerted by this person's hand as compared to the pressureprofile which was previously stored.

In FIG. 6 there is shown a typical pressure transducer in a plan view.Essentially the pressure transducer has a wafer 60 of silicon which iswell known. There is a layer 61 of silicon dioxide on the wafer on whichpiezoresistors 62, 63 are deposited by conventional techniques. Theresistors are positioned on the diaphragm region of the sensor andbasically piezoresistors vary resistance according to applied pressure.The resistor 62 and the remaining resistors as 63, 64 and 65 areconnected by the P+pattern conducting areas in a Wheatstone bridgeconfiguration. Such pressure transducers are well know and many examplesof such transducers exist and are manufactured by the KuliteSemiconductor Products, Inc., the assignee herein. See for example U.S.Pat. No. 6,577,224 entitled Ultrahigh Pressure Transducer, see also U.S.Pat. No. 6,642,594 entitled Single Chip Multiple Range PressureTransducer. Both patents name Anthony D. Kurtz, the inventor and bothhave been assigned to Kulite Semiconductor Products, Inc., the assigneeherein. As one can ascertain there are many other Kulite patents whichare pertinent to pressure transducers and which have been assigned tothe assignee herein.

In FIG. 7 there is shown the transducer of FIG. 6 together with a glasscover member or wafer 70. The glass wafer 70 has apertures therein whichare filled with a conductive material 73 to provide contacts for theWheatstone bridge. Thus contacts 73 and 74 enable one to obtain outputvoltages from the bridge which are directly proportional to appliedpressure.

In FIG. 8 there is shown a cross sectional view of the semiconductor,pressure sensor depicted in FIG. 7. The semiconductor sensor has acentral boss 80 which boss extends beyond the top surface of the siliconwafer layer 89. The piezoresistors as 81, 82, 83 and 84 are arranged ina Wheatstone bridge configuration as is well known. The bridge hascontact areas which are depicted by reference numerals 85 and 86. Thereis shown a thin interconnecting layer 95 which layer 95 contacts areas91 and 92 to provide direct contact to the terminals of thepiezoresistive bridge. In this manner the bridge can be biased and theoutput voltage can also be obtained. FIG. 10 shows a relatively simplediagrammatic sketch wherein piezoresistors 81 and 82 are shown in FIG.10 together with resistors 83 and 84 wired into Wheatstone bridgeconnection. The terminals for 85 and 86 receive bias voltage while theoutput terminals are directed to output leads 100 and 101. In a similarmanner the next pressure transducer designated by numeral 110 againreceives bias voltage and has output leads. Thus the layer 95 is aconnection sheet which serves to provide bias connections and outputleads for the entire pressure transducer array. The layer 95 is coveredby a thin plastic layer 90 which has the imprint of the hand formedthereon. As seen all the bosses are again coupled or otherwise securedto a ground plate 86 which basically is a stationary plate which may beconstructed from a rigid material. A pressure exerted upon the pressuresensor in the direction in arrow F depicted in FIG. 8 will cause adeflection of the transducer to enable an output voltage to be obtained.While the deflection plate is shown as plate 86 and the interconnectingplate is shown as plate 92 it is also understood that there are otherways of positioning the sensors between two plates. It is of courseunderstood that the imprint of the hand can be impressed on plate 86 andtherefore when a person places his hand on the plate it would touch anddepress the bosses 80 of the various sensors giving rise to an outputwhich is representative of all the sensors contacted. It is alsounderstood that one can also have an imprint of the hand on plate 90which again will cause the diaphragms to deflect. In a similar mannerthe sensors can be arranged in a matrix which can be formulated byintegrated circuit techniques on a single semiconductor chip taking theshape of various parts of the hand. It will thus become apparent to oneskilled in the art that there are many ways for implementing the presentinvention. Essentially the present invention discloses a method formeasuring tactical pressure when hand is placed on an instrumentedplate. The plate consist of a metal or plastic surface which is coveredwith a thin interconnecting layer. A large group of very small pressuresensors are mounted to the interconnection layer. The apertures on thereverse side of the sensors as for example apertures 87 may be filledwith a conductive epoxy or any other means to affix the sensors to theinterconnecting layer. The sensors have bosses on the front surface. Theheight of the boss, as indicated, is slightly elevated with respect tothe external surfaces of the sensor. Thus when a hand is placed on aplate it will touch and depress the bosses of the various sensors toprovide an output which is representative of all the sensors that arecontacted. One must be aware that there are many alternative embodimentswhich can be accommodated by the present invention and all are deemed tobe incorporated within the spirit and scope of the present invention.

FIG. 11 is a schematic diagram depicting an alternate embodiment of thepersonal identification apparatus according to this invention. In theabove description a replication matrix indicative of a hand templateemployed a plurality of pressure sensors distributed and located withinthe area of the template 11. While this approach has advantages, it isalso contemplated that the invention can operate without providing ahand template. In FIG. 11 there is shown a plate 110 which has pressuresensors positioned throughout the plate as for example sensors 112, 125,126, 130, 140 and so on. The sensors are arranged in an X-Y matrix. Thuseach sensor is defined by a row position X and a column position Y. Thismatrix addressing is well known. When a person to be identified placeshis hand 111 on the plate or pressure sensor matrix 110, pressure isexerted in the areas his hand covers. In other areas as 150 and 160 thepressure is zero. Thus by scanning the sensor array one will obtain theoutline of the person's hand as one can determine all zero pressureareas. While certain sensors within the hand area will also read zero alarge number of sensors within the hand area will record a pressure.Thus the hand outline is electronically provided. In this manner areasof concern can be determined within the hand area, for example, areas A,B, C and D of FIG. 4. Thus the array 110 is scanned (X,Y) by scanner115. This provides pressure signals to pressure measurement device 116.The device 116 receives the signals which are voltage levels from eachsensor in the array and stores scanned signals in a X-Y memory matrixwhich may be a ROM or other memory. The stored pressure profiles 116 arecompared with the ID stored profiles were obtained during enrollment. Acomparison is made via comparator 117. Based on known algorithms ifthere is a favorable comparison of pressure points, the person whose IDwas presented is positively identified and gains access to the securedregion or premises. It is understood that the processes described aboveare all under control of a microprocessor 119. The microprocessor 119can perform scanning, storage and comparison. It is, of course,understood that the hand template could be employed and thereforedepicted on plate 110 while using the scanner to scan the array withoutthe necessity of first determining the hand outline. Also shown is atemperature sensor 114. The temperature sensor is employed to confirmthe positioning of a human hand rather than a replica of a hand.Temperature sensors 114 can be randomly distributed within the handtemplate to confirm the presence of a human hand. This temperaturemeasurement can also be used with the individual in conjunction with thepressure reading.

Those of ordinary skill in the art may recognize that many modificationsand variations of the present invention may be implemented withoutdeparting from the spirit or scope of the invention.

1. A personal identification apparatus for measuring tactile pressuresexerted by a person's hand and indicative of his identity, comprising: amatrix plate having a plurality of pressure sensors distributed on saidplate, each operative to provide an output signal proportional to apressure applied to said plate at the area at which said sensor islocated, to enable said sensors to provide said output when a person'shand is emplaced on said plate to exert a pressure on said matrix,storage means for strong pressure profile signals of enrolled personsrequiring identification, means for comparing said stored pressureprofile with said output pressure signals to provide a favorablecomparison when said output signals conform to said stored profilesignals for positively identifying said person.
 2. The personalidentification apparatus of claim 1, wherein said pressure plate has atemplate of a human hand on a surface thereof, with said pressuresensors located within the area encompassed by said template.
 3. Thepersonal identification apparatus according to claim 2 wherein givenareas within said hand template contain more pressure sensors than otherareas of said template.
 4. The personal identification apparatusaccording to claim 1 wherein said sensors are arranged in an X-Y matrix.5. The personal identification apparatus according to claim 1 whereinsaid sensor employs piezoresistive elements arranged in a WheatstoneBridge configuration.
 6. The personal identification apparatus accordingto claim 4 further including: a scanner coupled to said X-Y matrix andoperative to scan said matrix by rows and columns to provide scannedoutput signals.
 7. The personal identification apparatus according toclaim 6 wherein said scanned output signals are stored in a memory. 8.The personal identification apparatus according to claim 1 furtherincluding a microprocessor operative to control said storage means andsaid means for comparing to enable pressure points to be compared undermicroprocessor control.
 9. The personal identification apparatusaccording to claim 1 further including temperature sensing means locatedon said plate and operative to measure the temperature of a human handemplaced on said plate.
 10. A personal identification apparatus formeasuring tactile pressures indicative of a person's identity,comprising: a replication matrix indicative of a template of a hand andcapable of accommodating typical variations of people's hand size, aplurality of pressure sensors distributed within said matrix, eachproviding an output signal when a person's hand is emplaced to exertpressure on said matrix, storage means for storing pressure profilesignals of enrolled persons having access to said personalidentification apparatus, means for comparing said provided outputsignals with said stored profile signal indicative of a person to beidentified to provide a favorable comparison when said output signalsconform to said stored profile signals for positively identifying saidperson.
 11. The personal identification apparatus according to claim 10,wherein given areas of said hand template contain a greater number ofpressure sensors than other areas.
 12. The personal identificationapparatus according to claim 10 wherein said pressure sensors arearranged in a X-Y matrix array.
 13. A method of performing personalidentification of a user who requires identification to be authorized,comprising the steps of: providing a matrix of pressure sensors on aplate to which said user's hand can be emplaced, first employing saiduser's hand on said plate to cause selective pressure sensors responsiveto the pressure applied by said hand to provide profile output signals,storing said output signals in a memory to obtain a hand pressureprofile for said user.
 14. The method according to claim 13 furthercomprising the steps of: second emplacing said user's hand on said plateto cause pressure sensors to provide output signals according to appliedpressure, and comparing said output signals with said stored signals toprovide a favorable comparison when said signals correlate indicative ofsaid user's identity to enable said user to be authorized.
 15. Themethod according to claim 13 further comprising the step of providing amatrix indicative of a hand template to accommodate various human handsizes.
 16. The method according to claim 15 comprising the step of:selecting predetermined areas within said hand template for monitoringsaid areas to a greater resolution than other areas within said handtemplate.
 17. The method according to claim 13 further comprising thestep of: scanning said matrix by row and column according to an X-Yaddress for each pressure sensor and to store said sensor outputaccording to said X-Y address.
 18. The method according to claim 13further comprising the step of: employing a microprocessor to controlthe storing of said output signals.
 19. The apparatus according to claim10 wherein said sensors are piezoresistive elements positioned on asilicon substrate and arranged in a Wheatstone bridge configuration. 20.The apparatus according to claim 19 wherein each sensor has a centralboss which extends above the sensor substrate surface and which bossreceives the applied exerted pressure to direct the same to saidpiezoresistors.